This is not only unfair but untrue. Your first part is right. Cap is seen as a figure who unapologetically chants "U-S-A!". He does so REGARDELESS of who the POTUS is, REGARDLESS.
You only demonstrate YOUR bias with your second untrue statement.
Captain America is apolitical.
CaptainCanada wasn't addressing the 'truth' of the character, but his public perception, particularly outside the U.S. He's a character who dresses in the American flag, after all, and such overt 'patriotism' has become associated with a particularly virulent strain of American politics and the attitudes such an allegiance entails. The nuances of the character actually on the page are something altogether different.
Fictitiously yours, Trent Roman