We do not have a 4.5% contribution, most of the NA contribution (as shown in the linked data) comes from Central America and the Caribbean. We contribute .25%.

The best strategy imho would be to split resources and do both. Helping far-off countries without cleaning up your own backyard would seem condescending and like an attempt to shift all blame elsewhere. Starting an effort to clean up ocean pollution originating from the US while simultaneously helping Asian countries do the same appears much more genuine and has a much better chance to work based on perception alone.

That's actually a really good point. While I do think that a larger share of effort and goodwill should be spent on major pollution first (and helping with cleanup and implementation of proper waste management there), not doing anything in your own backyard at the same time seems hypocritical.

why are they mutually exclusive?

Because even the U.S. does not have infinite resources.

Why does it require infinite resources?

Edit: I'm being glib, but seriously, this isn't necessarily a resource-intensive issue for the US to engage in. This kind of thing should be achievable purely through diplomacy. Surely there are some attractive incentives a nation like the US can bring to the table in the interests of compelling a nation like the Philippines to clean up its act, you know, like bringing a Nike executive to the meeting.