Snowplow and snowplough are both English terms.
Snowplow is predominantly used in 🇺🇸 American (US) English (en-US) while snowplough is predominantly used in 🇬🇧  British English (used in UK/AU/NZ) (en-GB).
In terms of actual appearance and usage, here's a breakdown by country, with usage level out of 100 (if available) 👇:
| Term | US | UK | India | Philippines | Canada | Australia | Liberia | Ireland | New Zealand | Jamaica | Trinidad & Tobago | Guyana | 
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| snowplow | 99 | 61 | 93 | 100 | 95 | 81 | 0 | 61 | 0 | 0 | 0 | 0 | 
| snowplough | 1 | 39 | 7 | 0 | 5 | 19 | 0 | 39 | 0 | 0 | 0 | 0 | 
Below, we provide some examples of when to use snowplow or snowplough with sample sentences.
(Examples are Wikipedia snippets under the CC ShareAlike 3.0 license.)