We previously has a website a.com (these are just example urls). We switched our main domain to b.com. A.com has been showing up in Google results even though the links redirect to A.com's homepage. Does this affect SEO or anything similar? It has been awhile, and we do not understand why a.com is still showing up. How long does it typically take to see a change in Google results for a domain name change? The content is nearly identical with a different layout.
See, Google takes upto 6 months for shifting all the credit to the new domain. Till the, your old domain might get reflected into search results. But don’t worry, if user clicks on your old domain he will be redirected the new one. I don’t think this will harm your new domain in any way.
I'm not entirely sure. I was brought onto the project after the redirect was put into place. If I search a.com and it automatically sends me to b.com, isit for sure a 301 redirect?
When you redirect your pages to a new page, it does not automatically changes the next day and will not show up as much as possible in Google SERPs. It will stay there and after a couple of weeks or months, depending on how will Google treat it, will you see the results and all the credits or link juice going to that page, will be passed to your new page.
Redirect may help but will not guarantee. Make sure your redirect pages per pages and help them out with new strong backlinks.