I was watching the blessings recited by clergy of various religions at the currently ongoing Republican National Convention to see if the blessings were made generally to G-d, or if the one giving the blessing would invoke powers antithetical to Judaism, such as the trinity.
Some were general, but there was (at least) one blessing that mentioned Jesus as a protector. Obviously, a Jew may not believe in or say amen to such a blessing. But may one answer amen to a blessing recited by one who believes the idea of Jesus as a power, but makes a general blessing to "god"?
Additionally, there was a blessing (from a Greek Orthodox priest) which made no mention of an additional power besides a god, but performed the Sign of the Cross as he was completing the blessing. Would this affect responding to his blessing?