not so much nationalism
I just disagree with you. NASA has in planning a much more ambitious future than ESA and better funding. Congress is always a threat but I think it will be politically impossible for America to abandon space. NASA will probably get approximately it's current funding level in real terms for the forseeable future. What it does with that budget is what counts.
I consider myself a human first. Future "martians" will also be humans. My patriotism is more reflected of my deep belief in democratic capitalism and western political values, not in defending NASA. I just call it like I see it.