I'm with WYSIWYG and Seamus on this one. You should say nothing to your relatives. Accept the gifts in the spirit in which they were given, and then give the clothes away to charity.

Your family in the U.S. aren't doing you any harm by sending you Christmas presents you don't really like. If the hints aren't working, just live with the situation. You could very well hurt their feelings if you try the blunt approach.

Edmund