It was ugly. It was gritty. It was dirty.

But the United States men’s national team prevailed in a physical contest with an unsportsmanlike El Salvador in a 2-0 victory to advance to the Gold Cup semifinals in Philadelphia on Wednesday. That is, in spite of a wrongly disallowed American goal and a series of embarrassing El Salvadoran cheap shots and nasty tackles somehow all missed by referee Drew Fischer and his crew.

Defenders Omar Gonzalez and Eric Lichaj — scoring their third and first international goals, respectively — got the points on the board in a frustrating and strange game against an opponent that pulled every dirty trick in the book to keep things somewhat competitive.

El Salvador played like it had nothing to lose — which indeed it didn’t, as the 103rd-ranked team in the world — in a feisty start, making the American defense uncomfortable with high pressure and quick combinations in the final third.

And all this energy very nearly resulted in an early goal as Lichaj sent a horrid back pass that Rodolfo Zelaya intercepted. A sharp intervention from Tim Howard prevented an early goal.

Clint Dempsey came close on the doorstep but was denied by Derby Carrillo. And Gyasi Zardes was onside by a decent margin when Dempsey sent him through and the Galaxy winger scored, but the flag went up to deny him the goal.

Before halftime, however, the Americans would get their goals. Michael Bradley drifted in a pinpoint free kick in the 41st minute and Gonzalez rose to it, even as Darwin Ceren tried to climb his back. Gonzalez got just enough of his flowing locks on the ball to beat Carrillo, who didn’t look good on the play.

In injury time, Lichaj foraged forward from right back and kept going. He did well to keep himself onside as Dempsey slipped him through splendidly and the right back beat Carrillo through his legs.

In the second half, Fischer lost control of the game as El Salvador reverted to the dark arts. Nelson Bonilla stuck his cleat through Lichaj’s standing leg and should have been sent off. Henry Romero bit Altidore in the shoulder on a corner, one play after twisting his nipple. All three of those moments warranted a red card.

But it wasn’t necessarily the woeful referee who kept El Salvador in the game. Rather, the malpracticing American defense was just as much to blame, bungling coverages and clearances with dismaying regularity.

All the same, El Salvador seldom got very close to a goal and as such, there was never much doubt that the U.S. would face a much more challenging Costa Rica in Dallas in the semifinals on Saturday.

Yet head coach Bruce Arena will nevertheless be left with concerns. Because for a fourth straight game in this tournament, the Yanks didn’t show much cohesion. This is partly a problem of Arena’s own making. He called in a B-team and shook up his lineup for each of the group stage games. Then, he drafted in six new players for the knockout stages — more than any other team still alive in the tournament, and six more than arch-rivals Mexico.

While the injection of talent was clearly necessary and apparent on Wednesday, there was no more discernible rhythm for having better players out on the field.

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This weekend, we’ll arrive at the business end of this tournament and the Americans are expected to at least reach the final, after falling short at the semifinal stage two years ago. Yet there is no recent evidence to suggest that this team should be considered a favorite against Costa Rica. Let alone in a would-be final against Mexico, although El Tri hasn’t exactly been convincing either.

The only thing that’s certain is that the Americans have run out of pushover opponents against whom they can afford to underperform. Displays such as Wednesday’s — on the defensive side of the ball, at least — likely won’t carry them much further in this bedeviling edition of the regional championship.

Leander Schaerlaeckens is a Yahoo Sports soccer columnist. Follow him on Twitter @LeanderAlphabet.

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