Here's the trick here:
Linked to x and link to x when said quickly will basically sound the same, leaving context aside, which, by the way, is what tells us whether link is meant as a present simple or simple past. The context always has something that follows.
- "linked to this" is pronounced link/t/o,then this. Just like: walk/t/. [final sound]
- "link to this" is pronounced link/t/o, also. Why? Because the to gets squished up against the link, so it ends up sounding the same as "linked to this".
Furthermore, the "to" becomes a quasi ta /æ/ [or /a/ in British English]: linkta this.
( I am only giving the sounds in the IPA alphabet for the t sound in linked and the ta sound in linked to x. Otherwise,it is too confused)
You can only differentiate the two by pausing:
These channels link to that channel. [slow and differentiated]
This channel linked to that channel [last week]. [slow and differentiated]
If you do not pause to emphasize the simple past, it simply will not be heard as simple past. So, in the sentences above, it is the "last week" that will tell your listener you are referring to something in the past.
- They walked to school every day. /t/
- They walk to school every day. no /t/
As the ed morpheme (syllable) is a /t/ sound, the next sound which is also that sound /t/ get absorbed into it. And the result is only one /t/ sound for "linked to" instead of the two which can clearly be seen in writing.
Same thing as link to and linked to. And though there may be a slight difference in the ta sound at the end, the squishing together (assimilation) of walked and to and walk and to is basically the same in BrE and AmE.
This issue is called co-articulation in phonology. How one phoneme sounds next to another. It is especially interesting in what is called "connected speech", which is the speech we all use in speaking everyday to each other.
Specifically, the issue you have brought up is called assimilation. When a sound like the ed in linked + to ends up sounding like link + to. That is called progressive assimilation. Naturally, when you slow down, you can make two /t/ sounds: one for link/t/ and the other for /t/o.
Here's an introduction to assimilation:
Speech is a stream of sounds rather than a series of discrete segments and in many cases the sounds merge or change, sometimes to anticipate the next sound and sometimes by being affected by a previous sound.
Assimilation refers to the effect where one sound segment is modified
by its neighbour, and causes one sound becoming phonetically similar
to the other. E.g. in English, in the sentence "I have to", the "v" of
"have" is devoiced and is pronounced as an "f" since the first sound
of the next segment is devoiced. When one sound changes to become more
like the next, this is "regressive" assimilation; when one sound
changes to become more like the preceding sound, this is "progressive"
assimilation. Crystal also notes "coalescent", where two sounds
mutually influence one another. Examples (from Crystal p166):
progressive : in "ten bikes", the "n" is pronounced as "m" regressive
: in "lunch score", the "s" is pronounced "sh" coalescent : in "don't
you", the center segment is pronounced "ch"
coarticulation and assimilation
[The maths issue is a different story. However, if you do not pronounce the th /θ/, you won't be saying it, just like you won't be saying bath or tooth is you don't pronounce the voiceless th in them.]