There are a couple different implications of owning US listed securities from a tax perspective.
First, there are dividends that come from these securities - for these you'll see a non-resident tax deducted from your account as a result of owning them within a non-registered account (Personal, Joint, or Corporate), TFSA or RESP. This is because these accounts are not recognized by the US. Despite this tax, there is no requirement to file any forms with the IRS.
Second, depending on how much you have invested in US listed securities, you may need to fill out a T1135. When the individual has the equivalent of $100K CAD or greater invested in foreign assets (i.e. US listed securities) this form is typically required. If you're not certain whether you should be filling out a T1135, we recommend consulting a tax professional!
Wealthsimple will produce a Foreign Asset Report regardless of the amounts you have with us so that come tax filing time so you can fill out the T1135 if needed.