Scepter and sceptre are both English terms.
Scepter is predominantly used in 🇺🇸 American (US) English (en-US) while sceptre 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 | 
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| scepter | 47 | 30 | 39 | 83 | 63 | 51 | 0 | 42 | 54 | 34 | 48 | 0 | 
| sceptre | 53 | 70 | 61 | 17 | 37 | 49 | 0 | 58 | 46 | 66 | 52 | 0 | 
Below, we provide some examples of when to use scepter or sceptre with sample sentences.
(Examples are Wikipedia snippets under the CC ShareAlike 3.0 license.)