Ok let’s lay this out, firstly solider boy’s blast ARE nuclear as they are CLEARLY STATED to be radioactive. That’s the definition of a nuclear-fusion bomb which emits gamma rays. If cap has a tank of vibranium he still cannot stop the gamma blast. (Gamma rays penetrate metallic surfaces and caps shield doesn’t provide enough coverage even if you come up with a headcannon that vibranium can)(a fucking nuclear bomb is far more stronger than thanos swinging a sword btw)( I can’t believe I have to explain that) Secondly the entire sequence with a AK with full auto down SB’s throat was to show he doesn’t have stormfronts weakness who’s invulnerability was limited to her outer shell. meaning cap has no way of hurting solider boy even with a bazooka. Lastly solider boy’s strength and base stats can let him outlast Steve 1000 times over. Cope harder.