I think it is very weird to have that tattooed or on any military gear. Secularism and such, but that is the heraldry of the former Kingdom of Jerusalem. Albeit being the result of crusades, I don't think it is supremacist by itself?

Edit: Also the flag of the country of Georgia. Going by this, the US military either serves in the Georgian army as of recent or they confused theirs with the country again?

Edit#2: Quick wikipedia, also apparently still the symbol of the Latin patriarchate of Jerusalem nowadays