If I was to operate high wattage European HPS lamps from 250w-1000w in the USA, can wiring combinations of American HX PSMH ballasts in parallel be ideal for operating these lamps assuming I use the appropriate ignitor?

Here is my approach to operating European high wattage HPS lamps in America:

SON-T/SON-E 250w:

wire US 150w M102 and US 100w M90 pulse start metal halide ballasts in parallel. This allows the 250w HPS lamp to operate at its proper 100v 3.0a.

SON-T/SON-E 400w:

wire 2 US 100w M90 pulse start metal halide ballasts and 1 US 150w M102 pulse start metal halide ballast in parallel. Runs the 400w HPS lamp close to its ideal current and voltage at 100v 4.2a rather than the proper 100v 4.5a.

SON-T/SON-E 600w:

wire 2 US 150w M102 pulse start metal halide ballasts and 2 US 100w M90 pulse start metal halide ballasts in parallel. Runs the 600w HPS lamp at 100v 6.0a rather than the 110v 6.0a it needs to operate at.

SON-T/SON-E 1000w:

wire 5 US 150w M102 pulse start metal halide ballasts and 1 US 100w pulse start metal halide ballast in parallel. Runs the lamp at 100v 10.2a rather than the ideal 110v 10.3a.

Should these paralleled American HX pulse start metal halide ballast combinations be ideal for operating the above European HPS lamps in America?

It should be OK. All HX have about the same OCV (this does not have to be exact, anything between 220..260V is fine), so the phase would be equal so the currents will directly sum up.
Maybe the 400W is marginal (-7%), but I think still within limits. Check it with Ameter once it runs the lamp.