First off, congrats on the Celestica position. Been a great company over the last 3-4 years.
Trimming is all a matter of personal preference and comfortability. Judging by your commentary, you seem a tad uncomfortable that it is that high, so in this sense, it could make sense for you to trim or maybe even implement a stop loss so that if it does fall a particular amount, you automatically trim it.
I know some people who are uncomfortable with particular holdings being 5% of their portfolio and I know some that don't mind a single company being 30%. So I can't really answer this question, it is solely up to you. What I will say is that if the allocation size and the fear of a pullback is bothering you, just get some peace of mind and trim it.
The second question ,again, comes down to personal preference. Keep in mind as well, over 60% of my portfolio is in "Canadian stocks" but the vast majority of those Canadian stocks have the majority of their business in the United States.